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Tubafore 03-23-2013 08:37 PM

Maximum roof overhang.
I am in the process of designing my home addition and have a gotten to the roof. The IRC gives a maximum of 24" for roof overhangs. Does this include drip edges that protrude or rain gutters, or is it just the wood structure?

Also I am putting rigid foam on the outside of my walls so I will have about 2 1/2" of material past the sheathing. Do I start measuring from the sheathing or the outer surface of the walls?


jagans 03-23-2013 08:56 PM

I would say 2 feet beyond the exterior of the structural wall. I would not worry about a 1x fascia. You going with EIFS?

Tubafore 03-23-2013 09:10 PM

No EIFS. The wall will be, studs>sheathing>rigid foam>furring strips>lap siding.
I wasn't sure if the 24" limit was purely a structural/roof loading concern. In which case I should exclude the non load bearing elements of the wall.

cleveman 03-23-2013 09:19 PM

This sounds like horse puckey to me. How can there be a building code telling you that you can only have a max. 2' soffit? There are plenty of 4' soffits around here, and I don't see any storm damage. A porch is not much different than an 8' soffit.

concretemasonry 03-23-2013 10:40 PM

The IRC is a national model code that can be adopted by reference by a state, county or city and is a minimum that can be made stricter by a local authority, but not to a lesser standard.

I would think that the "overhang" and what is included (drips, gutters, etc.) may be a zoning or property standard, but for structures, it is not worth splitting hais about.

If you have roof trusses designed for a home, they can be designed and supplied with a engineers structural adequacy for structural purposes even with an overhang from the structural wall that trumps the maximum, but you must respect the local zoning requirements.


ddawg16 03-23-2013 11:41 PM

My house has overhangs that are a little over 24" (as measured from the horiz).....considering that the rafters are 2x4's....24" is really pushing it....there is some obvious sag in some places. You don't want 2 people in the same spot. For my addition, I also went 24" but I used 2x6's...and 16" OC instead of 24" oc.

I don't think I would want to go over 24"....anything more would look 'odd'....

jagans 03-24-2013 04:48 AM

Are we talking trusses or stick framing? I would agree that over 2 feet would look a little strange, but I see where you are going. I guess you want 2 feet past the finished wall, as that makes sense vis a vis material use. Im sure a properly designed truss can handle that. Can you post the section in the IRC that refers to this?

Tubafore 03-24-2013 08:43 AM

This will be a cathedral ceiling with 2x8 rafters, reduced to 5 1/2" tall after being notched at the top plate. No ceiling joists so the rafters will be forming a cantilever to create the eaves. This should be strengthened by the frame that is built to hold the soffit in place.

The part of the IRC I saw, Although I look back now and realize it is in the section on steel roof framing.

"R804. Eave overhang. Eave overhangs shall
not exceed 24 inches (610 mm) measured horizontally"

Jodysimm 10-12-2014 04:10 PM

Overhang... inspections?
I recently asked my local building inspector a similar question. He didn't seem to care much either way. He thought I was splitting hairs. You could just ask your inspector. Or, since this is from last year, I assume it's already done. How did it all turn out?

The way I did it is I planned on having my 24" max but no more at every point an inspection was due. And, since I was allowed to apply siding before the framing inspection, and I was putting a rain screen and siding, I framed the roof such that I had 24" from the finished siding, before I applied my fascia or roof drip edge flashings. I personally don't think it's a possible thing to have too much overhang.

joecaption 10-12-2014 04:20 PM

I must be missing something.
I'm just not getting this trend of people going with foam on the outside.
It complicates everything from window and door installs, siding, and it's expensive, off gasses, toxic if it burns.
Just build it with 2 X 6 walls.

joecaption 10-12-2014 04:31 PM

I can see why someone may want a wider over hang in a warm sunnier climate, but why do you feel you need that much where you are?
I'd want that that sun in the windows and on the walls.

cleveman 10-12-2014 10:44 PM

I recently bought a home with 3' soffits, plus the gutter. It is a hip roof.

The siding is that crap masonite, and it is excellent condition, except the bottom of the first course. This siding is 50 years old.

So that is a reason to have a deep soffit (and a hip roof). It protects the siding (and the windows). It also keeps the area around your home as dry as a bone.

Tubafore 10-13-2014 12:47 PM

My main reason for going with foam on the outside is because it made it easier to structurally integrate the addition with the existing house and add some R value to the old portion of the house by foaming and residing everything at the same time.

The window and door installs were not that complicated even for an amateur like myself.
It wasn't that expensive either. After accounting for cheaper studs and batts the foam only added $25 per 100 sq ft compared to 2x6 walls. Any off gassing is on the outside of the walls and will escape through the siding. If my walls are on fire the toxic fumes are again on the outside of the walls.

The rated R value is the same as 2x6 walls but effectively will be better because the foam breaks thermal bridging that happens through the studs. I take this to be the main reason for the foam on the outside trend.

Colorado is a warm sunny climate in the summer. It's not uncommon for us to have stretches of days or weeks with temps in the upper 90's. I want that sun off my walls. In winter time with the sun lower on the horizon larger overhangs will not block the sun at all.
Larger overhangs also keep water off your walls windows and doors. Everything lasts longer. Less chance for rot.

Jodysimm 10-15-2014 03:22 PM

Reason for lots of overhang
I design with as much overhang as possible to protect the structure from rain. I live in a rain forest climate zone. I try to design with a flat torch on roof, with a small wall around the edge and drains. I drain into ABS and pipe it away from the structure. The long overhang shades the sun in the summer when the sun is high in the sky, and in the winter up here in the BC Interior, around 50 degrees latitude, the sun comes in low over the horizon in the wintertime. I'd go way more overhang if it was allowed. I think sometimes you can do it if you shell out for an engineer. I see people around town here with much bigger overhangs. I'm going to ask the inspector how to get around the IRC regulation next time I'm in the design phase.

Jodysimm 10-15-2014 03:23 PM

Also, keeping preciptation far away from your structure should reduce frost heaving, foundation leakage etc. I have a crawl space and it's dry as dust under there even in the middle of winter.

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